Donald Trump’s presidential transition hit a squall this week over his potential selection of Mitt Romney as Secretary of State. Opposition to Mr. Romney among some Trump campaign advisers has broken out in public, while former New York Mayor Rudy Giuliani is playing up his campaign loyalty to Mr. Trump as he lobbies to be America’s top diplomat.

Our preference would be Mr. Romney over Mr. Giuliani, but if the debate is that disruptive then Mr. Trump would be better off going to someone else. Choosing Mr. Romney would reassure U.S. allies and signal that Mr. Trump is reaching across the GOP to populate his Administration.

Yet more than a few Trump loyalists mistrust Mitt for his caustic criticism of Mr. Trump during the GOP primaries. They fear he won’t be loyal if he gets the job, though presumably the two men would hash that out in advance. One virtue of choosing Mr. Romney would be to get his candid views, and if his loyalty would always be in question for doing so, then he shouldn’t take the job.

As for Mr. Giuliani, his campaign role isn’t by itself enough to earn such a crucial post. The former prosecutor lacks foreign-policy experience and his extensive list of overseas business clients could become a confirmation problem if they aren’t thoroughly vetted. Another question is whether Mr. Giuliani could manage a State Department bureaucracy that would oppose him and the Trump agenda.

Which leads to other potential choices. One is John Bolton, who was a senior and successful State Department official under Presidents George H.W. Bush and George W. Bush. He understands the job, and he knows from hard experience the tricks that the State bureaucracy plays. He has a blunt style that we suspect Mr. Trump might find refreshing.

Another name worth considering is former General and CIA Director David Petraeus. The architect of the 2007 surge that defeated al Qaeda in Iraq, Mr. Petraeus has a far-reaching strategic vision and long experience massaging allies and staring down foes. He understands when diplomacy is required but also when military force is needed to achieve diplomatic goals.

Democrats might make an issue of Mr. Petraeus’s misdemeanor conviction for turning over classified information to a biographer who was also his paramour. That mistake cost him his job at CIA. But he has apologized and paid a price, and the U.S. shouldn’t be denied his talents for that one mistake.

His selection could also put three former generals atop the main foreign-policy portfolios, along with former Lt. Gen. Michael Flynn as national security adviser and the widely mooted choice of former Gen. James Mattis to run the Pentagon. Gens. Mattis and Petraeus are about as widely read and strategic thinkers as you’ll find, in or out of the military, so this strikes us as a needless concern.

More important is the message these choices would send to allies and adversaries. Mr. Trump is inheriting a far more dangerous world than any President since Ronald Reagan. Authoritarians are pressing to dominate Eastern Europe, the Middle East and Western Pacific. As a Commander in Chief who will be getting his own on-the-job training, Mr. Trump needs counselors who know their briefs from the first day. At least on national security, experience should trump loyalty.”